The present invention relates generally to silk screen type printing machines, and more particularly to those described in French Pat. No. 1,263,239 and 1,315,719 which correspond generally to U.S. Pat. No. 3,090,300, incorporated herein by reference.
As is well known silk screen printing machines comprise a so-called silk screen of silk or another suitable fabric which forms a stencil is applied against an article to be printed and a squeegee associated with the screen and adapted to force ink through open meshes in the screen. In case the article to be printed is cylindrical the silk screen is subjected to translational reciprocation and the squeegee is held stationary, but when the article to be printed is flat the silk screen is held stationary and the squeegee is subjected to translational reciprocation.
It is also well known that it is necessary, after printing an article in a silk screen printing machine, to effect the disengagement of the silk screen relative to the article so as to enable the removal of the article and also to effect, concurrently, the relative disengagement of the squeegee with respect to the silk screen so as to permit the return stroke of the silk screen or the squeegee, depending on which reciprocates.
In the printing machines described in the above identified patents this problem is simply and satisfactorily solved by securing the silk screen to a carriage mounted for movement on two parallel bars which constitute the forward links of a four-bar linkage the rear links of which are the bars on which a drive carriage is mounted, the drive carriage being connected for translation with the silk screen supporting carriage for printing cylindrical articles, and by securing the squeegee to a vertical leg of a right-angled bracket which itself constitutes a carriage mounted for movement on the bars forming the forward and rear upper links of the four-bar linkage, which carriage is itself adapted to be connected for translation with the drive carriage, for printing flat articles.
After printing an article, whether it is flat or cylindrical, the forward links of the four-bar linkage carrying the screen and squeegee carriages are lifted vertically and simultaneously thereby disengaging or separating the screen with respect to the article to be printed and relatively disengaging or separating the squeegee with respect to the screen, precisely as desired.
But in machines of this type in which the disengagement or separating movement of the squeegee is effected mechanically by utilizing mechanical means which assure moreover the disengagement of the screen, it is necessary, keeping in mind that the squeegee carriage must be connected for translation with the drive carriage, to form the screen supporting carriage of two sufficiently spaced bracket arms so that the right angle bracket defining the squeegee carriage may be disposed therebetween. In other words, the connecting means provided for connecting the squeegee for movement with the bar forming the forward upper link of the four-bar linkage is connected to this bar at a point between the two bracket arms which, interconnecting the forward upper bar to the forward lower bar, defines in combination the screen carriage.
Inevitably the maximum permissible stroke of the screen carriage along the bars is determined, independently of the length of these bars, by the presence of the squeegee carriage between the bracket arms which make up the screen carriage; in the machines of this design, the screen carriage has, then, a limited stroke when printing cylindrical articles.